The lenses of the cephalic eyes resemble much those of the preceding species though more elongate and ovate. They are covered by a membrane which surrounds their upper moiety and between the lenses joins the interstitial test. In the horizontal section these membranes surround the lenses as an annular wall.
Phaëtonides Barr.
Ph. Stokesi Murch.
The hypostoma somewhat reminds of that of Calymmene, has projecting angles and a prominent knob below the straight anterior border. The two oblique and oblong macula are tubercular and placed near the lateral borders. This hypostoma is upon the whole much related to that of Phillipsia and Proetus.
Phillipsia Portlock.
De Koninck figured a hypostoma of Phillipsia in his »Description des Animaux Foss. de Belgique» as Cyclus Brongniartianus pl. LII fig. J and Novák in III figs. 6, 7 copied it and corrected the error. It is provided with two globular maculæ united by a curved ridge.
Phillipsia Eichwaldi Woodw. Novák III fig. 5 a hypostoma with globular maculæ. We have been able to examine three different, unnamed or undeterminated species, which we distinguish by numbering them.
Phill. No. 1 from the Keokuk group of Crawfordsville, N. America. The hypostoma is broader than in the other species. The nearly horizontal elongated maculæ placed near the median line, close to the lateral margins.
Phill. No. 2 ([pl. VI, figs. 15-18]) probably from the Carboniferous formation of Belgium is of a lengthened form. The elliptic maculæ in the groove, below the central elevation. They are smooth and surrounded by a flat border.